Hydrous zirconium oxide dehydration catalyst

ABSTRACT

Disclosed is a hydrous zirconium oxide catalyst for the dehydration of alcohols of the general formula ##STR1## to terminal olefins, as well as a method for preparing said catalyst. The catalyst provides high conversion of alcohol to olefin, high dehydration selectivity, and high selectivity for terminal olefin.

This is a divisional of application Ser. No. 542,278, filed Jun. 22,1990 now U.S. Pat. No. 5,130,287.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydrous zirconium oxide dehydrationcatalyst and a method for producing a compound having a double bond atthe terminal position (hereinafter referred to as a "terminal olefin" or"α-olefin") using such a catalyst.

2. Description of the Prior Art

The present invention relates to a method for producing a terminalolefin. More particularly, the present invention relates to a method forproducing the terminal olefin by dehydration of a compound representedby the formula (I) ##STR2## wherein R is a C₂ -C₂₀ hydrocarbon groupwhich may have one or more double bonds.

It is hitherto well known that an olefin can be produced by dehydrationof a compound represented by the formula (I). The details of the methodcan be taken, for example, from J. Am. Chem. Soc., 85, 2180 (1963), orfrom Oil Chemistry, 17, 236 (1968) It is also known from DE-A-144 362and the corresponding CH-A-721077 that zirconium oxide can be used as acatalyst in the dehydration of secondary alcohols. European PatentSpecification Publication No. 150,832 also discloses that high purityzirconium oxide, which has a total content of silicon and titanium(expressed as dioxides) of 0.3% by weight or less, is useful as adehydration catalyst. In addition, European Patent ApplicationPublication No. 0222356 discloses the dehydration of 2-alcohols toterminal olefins using a zirconium oxide catalyst treated with analkaline solution. Thorium oxide is known as a catalyst for theselective production of the terminal olefin, but its use in industry isdifficult because thorium is a radioactive element so that there occursa serious problem of safety in handling thorium oxide as a catalyst.

Many prior art dehydration catalysts generally suffer from the followingdisadvantages:

(1) the internal olefin is mainly produced and the selectivity of theterminal olefin is low, especially at high conversion;

(2) the alcohol is converted into a significant amount of ketone (aswell as olefin); and/or

(3) the catalyst contains a radioactive element so that there is aproblem of safety.

A catalyst has now been discovered which overcomes the drawbacks of theprior art dehydration catalysts by providing high selectivity forα-olefins while at the same time eliminating the problems attendant withradioactive materials.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a method ofmaking a hydrous zirconium oxide dehydration catalyst comprising:

A. dissolving zirconyl nitrate in water;

B. hydrolyzing the zirconyl nitrate with ammonia at elevated temperatureuntil substantially all of the zirconyl nitrate is hydrolyzed to hydrouszirconium oxide;

C. recovering the hydrous zirconium oxide and washing it with aqueousammonium hydroxide until the hydrous zirconium oxide is essentially freeof nitrate ions;

D. washing the hydrous zirconium oxide with water until it isessentially free of ammonium ions; and

E. drying the resulting product at elevated temperature until it isessentially free of water.

The present invention also provides the product of this process.

There is also provided in accordance with the present invention, adehydration catalyst comprising hydrous zirconium oxide which isessentially free of nitrate ions, ammonium ions and water.

Further provided in accordance with the present invention is a methodfor producing a compound having a terminal double bond comprisingdehydrating a compound having the general formula ##STR3## wherein R isa C₂ -C₂₀ hydrocarbon group in the presence of a dehydration catalystcomprising hydrous zirconium oxide which is essentially free of nitrateions, ammonium ions and water.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The starting material used in the dehydration method of the presentinvention is a compound represented by the general formula ##STR4##wherein R is any of C₂ -C₂₀ hydrocarbon groups, which may have doublebonds, are preferably C₂ -C₁₀ hydrocarbon groups, more preferably C₂-C₁₀ saturated hydrocarbon groups. When the present invention is carriedout by using such a starting material, a terminal olefin is selectivelyproduced through the elimination of both the hydroxyl and a hydrogen ofthe methyl shown in formula (I), forming water.

Examples of the compounds represented by formula (I) include, but arenot limited to, 1-cyclohexylethanol 4-methyl-2-pentanol and 2-hexanol.

The dehydration catalyst of the present invention is prepared bydissolving zirconyl nitrate in water and hydrolyzing the dissolvedzirconyl nitrate with ammonia at an elevated temperature, i.e., about50° to about 75° C. A precipitate (hydrous zirconium oxide) forms whichis recovered and washed thoroughly with aqueous ammonium hydroxide untilthe precipitate is essentially free of nitrate ions. The precipitate isthen washed with water until the precipitate is essentially free ofammonium ions. Finally, the precipitate is dried, e.g., at about 80° C.or higher, preferably under vacuum, until the precipitate is essentiallyfree of water, e.g., for at least about 16 hours. The resulting productis hydrous zirconium oxide which is essentially free of nitrate ions,ammonium ions and water. As used herein, the term "essentially free"means that the catalyst contains about 0.1 wt % or less of theparticular material. Before use, the catalyst is calcined at about 350°to about 650° C. for a period of generally about 0.1 to about 50 hours,preferably about 1 to about 10 hours.

It has been found that the catalyst of this invention may be used inadmixture with other metal oxides while still achieving high conversionof alcohol to olefin, high selectivity for dehydration, and highselectivity for production of terminal olefin. Thus, the catalyst cancontain up to about 15 wt % of a rare earth oxide (such as cerium,ytterium, europium and lanthanum oxide), yttrium oxide or hafnium oxide.On the other hand, some other metal oxides reduce the effectiveness ofthe catalyst of the present invention. These include titanium, zinc, andindium oxides.

In the present invention, the dehydration reaction is carried out asfollows: while the mode of reaction is not particularly restricted, afixed or fluidized catalyst bed/vapor-phase reaction system is adopted.The reaction temperature is generally from 200° to 500° C., preferablyfrom 300° to 400° C. The reaction pressure is also not particularlyrestricted; the reaction can be effected under atmospheric or slightlyelevated pressure. If necessary, the vapor of feed compound (I) isdiluted with an inert gas such as nitrogen gas before reaction. Thereaction under reduced pressure also gives good results. The materialfeed rate expressed in LHSV is generally from 0.1 to 15 hr⁻¹, preferablyfrom 0.5 to 5 hr⁻¹.

When the catalyst of the present invention is employed in thedehydration of the above-described alcohols, high conversion of alcoholto olefin, high selectivity for dehydration, and high selectivity forthe production of terminal olefin are all achieved. Typically,conversion of at least about 60%, dehydration selectivity of at leastabout 90% (and often at least 95%), and terminal olefin selectivity ofat least about 65% are obtained when the catalyst of this invention areused.

The following examples illustrate the present invention in more detailwithout limiting the scope of the invention.

COMPARATIVE EXAMPLE A

The following procedure for preparing a zirconium catalyst correspondsto literature descriptions.

Zirconyl nitrate (57.8 g) obtained from J. T. Baker Chemical Co. wasmixed with 500 g of distilled water in a creased Morton 1000 mLround-bottom flask fitted with a stirrer, thermometer, and additionfunnel. The mixture was stirred vigorously at 25° C. and blanketed withnitrogen. Ammonia (30%, Mallinckrodt, 245 g) was added over a period of5 minutes and stirring was continued for 15 minutes.

The resulting mixture was placed in two centrifuge bottles andcentrifuged at 3000 rpm for 15 minutes. The supernatant liquid wasdecanted off; 250 mL of distilled water was added to each bottle andmixed thoroughly before centrifuging again. This was repeated five timesat which point the wash water was at pH 7.

The precipitate was dried in an oven under nitrogen at 120° C. for 16hours. The resulting powder was compressed into 10-30 mesh particles touse as a dehydration catalyst.

The catalyst (4 g) was packed in a 1/2 inch diameter quartz tube andcalcined in nitrogen at 600° C. for 4 hours. 2-Hexanol (0.5 mL/hour) waspassed over the catalyst at 300° C. in a nitrogen flow of 3 mL/minutefor 6 hours. During the last 3 hours of this time, a sample wascollected with the results shown in Table A. The conversion anddehydration selectivity were satisfactorily high, but the 1-hexeneselectivity was undesirably low.

COMPARATIVE EXAMPLE B AMD EXAMPLES 1 AND 2

Three more experiments using the Baker zirconyl nitrate were made inwhich the ammonia addition and washing parameters were changed fromthose used in Comparative Example A. In Comparative Example B, theammonia addition was conducted at 50° C.; in Example 1, the ammoniaaddition was also conducted at 50° C., but additional washing of theprecipitate first with 15% ammonia and then with water was employed; andin Example 2 the ammonia addition was conducted at 75° C. and theadditional washing with ammonia and then water (as in Example 1) wasemployed. The results of cracking 2-hexanol using these catalysts areindicated in Table A.

EXAMPLE 3

In this experiment, the Baker zirconyl nitrate mixture with water washeated for 1-hour at 50° C. and centrifuged to remove undissolvedmaterial before the ammonia addition. Approximately half the materialwas removed indicating that this source of zirconyl nitrate had alreadybeen partially hydrolyzed. Precipitation and washing parameters were asin Example 1. The hydrous oxide obtained was dried at 80° C. under 15in. Hg vacuum for 16 hours. The derived catalyst gave good results asseen in Table A.

EXAMPLE 4

This experiment was done as in Example 1, except that the zirconylnitrate which was obtained from Aldrich Chemical Company was fullysoluble, and that the hydrous oxide was dried under vacuum.

Aldrich zirconyl nitrate (57.8 g) was dissolved in 250 g of distilledwater at 50° C. Ammonia (122 g of 15% ammonia) was added over 30minutes. The mixture was digested at 50° C. for 90 minutes. Theresulting precipitate was first washed with 250 mL of 15% ammonia threetimes with the last ammonia wash sitting overnight; then with wateruntil the pH reached 7; and then with two more water washes. This finalhydrous oxide was divided into two parts as shown in Table A. The firstpart (Example 4a) was dried under vacuum as in Example 3. The secondpart (Example 4b) was dried under vacuum at a higher temperature (120°C.) for a longer time (48 hours).

As seen in Table A, both dried oxides gave good cracking results--thefirst part gave results very similar to Example 3 and the second, whichhad been more exhaustively dried, gave even better 1-hexene selectivity.

EXAMPLE 5

This experiment was a repeat of Example 4b except that the hydrous oxidewas calcined at 550° C. and the cracking was performed at 290° C. Theselectivity results shown in Table A were very good.

EXAMPLE 6

This experiment was a repeat of Example 4b except that the precipitatewas digested in the ammonia for only 15 minutes instead of 90 minutes.

The cracking results were significantly different. At 300° C., theconversion was very high at 99.9% and dehydration selectivity was veryhigh at 99.8%, but the 1-hexene selectivity was unsatisfactory at only49%. When the cracking temperature was lowered to 260° C. and conversiondropped to 13%, the dehydration selectivity dropped to an unsatisfactory91%, while the 1-hexene selectivity was still poor at 59%.

EXAMPLE 7

A similar experiment to Example 4b was run in which the digestion timewas 1200 minutes and the drying time was 72 hours. Good cracking resultsof 94% conversion, 99.5% dehydration selectivity, and 78% 1-hexeneselectivity were obtained at 300° C.

                  TABLE A                                                         ______________________________________                                        HYDROUS ZIRCONIUM OXIDE PRECIPITATES                                          CATALYST       2-Hexanol Cracking.sup.1                                       FROM           Temp.,  Conver-                                                                              Dehydration,                                                                           1-Hexene,                              EXAMPLE        °C.                                                                            sion, %                                                                              %        %                                      ______________________________________                                        A.sup.2        300     64     98       41                                     B.sup.2        300     53     97.5     56                                     1.sup.2        300     88     99.2     65                                     2.sup.2        300     96     98       72                                     3.sup.3        300     91     97       77                                      4a.sup.4      300     99.3   98       80                                      4b.sup.4      300     84     99.5     88                                     5.sup.4        290     73     99       90                                                     300     99.9   99.8     49                                    6.sup.4                                                                                      260     13     91       59                                     7.sup.4        300     94     99.5     78                                     ______________________________________                                         .sup.1 Sixhour test, catalyst first calcined 4 hours at 600° C.        .sup.2 Starting material: relatively insoluble ZrO(NO.sub.3).sub.2 from       Baker.                                                                        .sup.3 Insoluble ZrO(NO.sub.3).sub.2 removed before precipitation.            .sup.4 New source of ZrO(NO.sub.3).sub.2 : Aldrich, all soluble.         

EXAMPLE 8

Hydrous zirconyl oxide precipitates were prepared in accordance withExample 4b with varying amounts of other metal salts (mainly nitrates)present, thereby preparing the cogel oxides listed in Table B. Theresults of dehydration reactions using these catalysts are alsoindicated in Table B.

                                      TABLE B                                     __________________________________________________________________________    HYDROUS ZIRCONIUM OXIDE/METAL OXIDE CATALYSTS                                              2-Hexanol Cracking                                               Metal Oxide  Calcine,                                                                              Cracking,                                                                           Conversion,                                                                          Dehydration,                                                                         1-Hexene,                            In Catalyst, Amount                                                                        temp(°C.)                                                                      temp(°C.)                                                                    %      %      %                                    __________________________________________________________________________    Yttrium oxide, 5 wt %                                                                      600     300   88     96     91                                   Yttrium oxide, 5 wt %                                                                      350     300   96     99     77                                                         290   97     97     85                                  Yttrium oxide, 5 wt %                                                                      450                                                                                   300   99     96     84                                                         290   96     98.5   86                                  Yttrium oxide, 5 wt %                                                                      550                                                                                   300   98     96     82                                                         290   99     99     89                                  Yttrium oxide, 5 wt %                                                                      .sup. 600.sup.5                                                                       300   99     98     88                                   Yttrium oxide, 15 wt %                                                                     600     300   75     97.5   87                                   Yttrium oxide, 100 wt %.sup.6                                                              600     300   89     90     90                                   Hafnium oxide, 5 wt %                                                                      600     300   94     99     83                                   Cerium oxide, 5 wt %                                                                       600     300   81     99     88                                   Ytterbium oxide, 5 wt %                                                                    600     300   100    99.9   76                                   Europium oxide, 5 wt %                                                                     600     300   80     99.4   81                                   Lanthanum oxide, 15 wt %                                                                   600     300   99.3   95     77                                   Titanium oxide, 5 wt %                                                                     600     300   86     99.8   59                                   Zinc oxide, 5 wt %                                                                         600     300   99.5   32     71                                   Indium oxide, 5 wt %                                                                       600     300   99     13     74                                   __________________________________________________________________________     .sup.5 Calcined in the presence of water.                                     .sup.6 No hydrous zirconium oxide in catalyst.                           

The data in Table B shows that the presence of rare earth oxides,yttrium oxide and hafnium oxide in the catalyst does not adverselyeffect catalyst performance significantly. However; the presence oftitanium, zinc and indium oxides does significantly impair catalystperformance.

What is claimed is:
 1. A method for producing a compound having aterminal double bond comprising dehydrating a compound having thegeneral formula ##STR5## where R is a C₂ -C₂₀ hydrocarbon group, in thepresence of a dehydration catalyst comprising the product produced bythe method comprising:A. dissolving zirconyl nitrate in water; B.hydrolyzing the zirconyl nitrate with ammonia at elevated temperatureuntil substantially all of the zirconyl nitrate is hydrolyzed to hydrouszirconium oxide; C. recovering the hydrous zirconium oxide and washingit with aqueous ammonium hydroxide until the hydrous zirconium oxide isessentially free of nitrate ions; D. washing the hydrous zirconium oxidewith water until it is essentially free of ammonium ions; and E. dryingthe resulting product at elevated temperature until it is essentiallyfree of water other than water which is chemically bound to the hydrouszirconium oxide.
 2. The method claim 1 wherein the dehydration catalystis calcined prior to its use in the dehydration reaction.
 3. The methodof claim 1 wherein the compound dehydrated is 2-hexanol and the compoundhaving the terminal double bond is 1-hexene.
 4. The method of claim 1wherein the catalyst further comprises up to about 15 wt % of a rareearth oxide, yttrium oxide or hafnium oxide.